Background technology
Cold-work die steel is mainly used in and is manufactured on the mould that carries out press forming under cold state (room temperature) condition, like cold stretching mould, cold-heading mould, cold extrusion die, impressing mould, rolling die etc.The working conditions of cold-work die is similar a bit with cutlery, but because of machined material is out of shape under cold conditions, so resistance to deformation is very big.Compare with Cutlery Steel, cold-work die steel should require higher hardening capacity, wear resistance and toughness, and the requirement of red hardness can be hanged down, and the temperature rising can be above 200-300 ℃ when general cold-work die was worked.
At present, using the most widely on the domestic moulding stock market, cold working die steel material is that high carbon and chromium cold-work die steel Cr12MoV is as the universal cold working die steel material of main separation.This steel has higher hardening capacity, hardenability, wear resistance; High-temperature oxidation resistance is good; Can be used as universal cold working die steel material and be used to make the cold-work die of various uses, for example complex-shaped punching concave die, cold extruding die, roll threading wheel, cold shears cutting knife and precision measuringtoll etc.But (this material chemical composition mass percent is: C:1.45-1.70%, Si≤0.40% to contain higher carbon and chromium element during the alloying element in the universal cold working die steel material of this Cr12MoV is formed; Mn≤0.40%, Cr:11.0-12.5%, Mo:0.4-0.6%; Ni≤0.10%, Cu≤0.10%, P≤0.030%; S≤0.030%), and too much carbon and chromium constituent content can make and have netted ledeburite carbide in the material microstructure, causes the toughness of material not high.Mould in use is prone to tipping, ruptures or subsides.
The performance index of Cr12MoV steel quench through 980 ℃ and 200 ℃ of tempering after, ballistic work is 39J, hardness is 60HRC.And these performance index are key technical index of cold-work die steel.
Cold-work die is mainly used in the cold-forming of metal or non-metallic material, comprises cold stamping, cold extrusion and cold-heading etc.This type mold work load is big, dimensional precision, surface quality require high.Usually the cold-work die steel of selecting for use requires enough intensity, toughness, hardness and wear resistance.And the Cr12MoV steel contains uneven ledeburite carbide in organizing, though through after quenching and the tempering higher hardness and wear resisting property being arranged, toughness is lower.Burst apart and subside easily in actual use.
Above-mentioned Cr12MoV steel adopts arc melting, is cast into the steel ingot hammer cogging, and concrete steps are followed successively by steel-making, forging, thermal treatment, form product at last.Its forged Heating temperature is 1110-1130 ℃, and final forging temperature is >=900 ℃, and the type of cooling adopts high temperature annealing, the cold or sand cooling in hole.Because the Cr12MoV steel forms a large amount of thick eutectic carbidess that are continuous net-shaped distribution.This netted eutectic carbides seriously isolates matrix, formation of crack and crack propagation approach when also can be used as the die steel fracture, thus making the serious embrittlement of crystal boundary of die steel, toughness is very low.And when forging, owing to receive the restriction of forging ratio, for the large size strand, the eutectic carbides of its heart portion is difficult to smash, so often have banded carbide segregation in the die steel tissue after forging, makes the performance of die steel anisotropy occur.And because the waste product that cracking and burning etc. cause appears in the existence of netted eutectic carbides easily in forging process.
CN1854324A discloses a kind of production technique of cold work die steel in high alloy through.Its Chemical Composition weight percent content is: C:1.45-1.55%, Cr:7.8-8.2%, V:3.9-4.1%, Mo:1.4-1.6%, Si:0.9-1.1%, Mn:0.3-0.5%, surplus Fe.This cold-work die steel contains higher carbon and molybdenum, v element, and adopt spray forming technology, a time reaches the deflection hot rolling and the isothermal spheroidizing thermal treatment process is produced.But this cold work die steel in high alloy through does not relate to toughness.
CN101182619A discloses a kind of high toughness cold working die steel and method of manufacture thereof.Its Chemical Composition weight percent content is: C:0.9-1.0%, Cr:9-10%, V:0.8-1.0, Mo:2.0%, Si:1.0%, surplus Fe.Mainly be the carbide reinforced effect that relies on Cr, improve the hardness of material, but, be not very desirable thereby cause the toughness of steel owing to carbon, chromium are prone to form a large amount of primary carbides in process of setting.
For this reason, a kind of high-intensity high-tenacity is provided, the wear-resisting cold-work die steel that is suitable for cold-forming precision stamping mould cold forging, trolley part bending mould, shaped by fluid pressure mould has crucial meaning.
Embodiment
Specify characteristics of the present invention and advantage below in conjunction with embodiment.
Among the present invention, unless otherwise, content all refers to weight percent content.
In order to realize the purpose that high tough high wear-resisting cold process die steel is provided of the present invention, each principal element is controlled as follows:
C:0.85-0.95%
The C carbon is one of main chemical elements of high-strength toughness cold working die steel; It is the indispensable fundamental element that forms various carbide such as vanadium carbide, molybdenum carbide and chromium carbide; Also be the important element of homogeneity of structure that influences component segregation and the steel of steel, be dissolved in and guarantee in the martensite that martensite has good intensity and hardening capacity.Carbon content increases in the steel, and yield-point and tensile strength raise, but plasticity and impact reduce.In addition, carbon can increase the cold shortness and the timeliness susceptibility of steel.The design's composition of steel is compared with the Cr12MoV steel, and carbon content has bigger reduction, its objective is the distribution and the character of the carbide in the microstructure of improving steel, improves the rank of the carbide network of steel.Lower carbon element content can prevent that thereby steel from producing the segregation tissue and causing the bending strength of steel and impelling strength to descend in the process of solidifying.Therefore,, will cause the formation of too much carbide and the segregation of tissue to produce, influence the netted performance index of steel, and particularly cause the bending strength of steel and impelling strength to reduce if carbon content is higher than this composition design upper limit; But this composition Design scope that is lower than carbon also will cause carbon and other alloying elements to combine to form the equivalent generation deviation of carbide; The stable tiny carbide and the compound action of carbide be can not form effectively, the intensity of steel and the hardenability of steel influenced.Therefore, control C:0.85-0.95% among the present invention, preferably control C:0.86-0.94%.
Si:0.45-1.0%
Si is dissolved in the matrix can improve matrix strength, and can hindering martensitic decomposition during tempering, to have improved the tempering of steel stable, in steelmaking process, can play the effect of reductive agent and reductor.If silicon content surpasses 1.0% in the steel, even if the silicon alloying element.Silicon can significantly improve the elastic limit of steel, yield-point and tensile strength.Element silicon can effectively hinder martensitic decomposition in the drawing process of austenite after martensitic transformation, this mainly is through the growing up and enlarge the εTan Huawu stable region of the εTan Huawu particle of drawing up, has postponed εTan Huawu to Fe
3The transformation of C.The control of silicone content of the present invention Cr12MoV steel relatively at present has raising slightly, and purpose is further to stop the decomposition in drawing process after the martensitic transformation, has certain effect to improving the bending strength and the impact property value of steel after quenching.Therefore, control Si:0.45-1.0% among the present invention, preferably control Si:0.55-1.0%.
Mn:0.2-0.4%
Mn is in the process of austenitizing, and major part has been added in the middle of the matrix, has improved the alloy content in the matrix, has strengthened the solution strengthening effect, thereby improves the intensity of matrix.But Mn has serious positive segregation tendency, can be enriched in eutectic cell crystal boundary place and form the intergranular carbide, can reduce the toughness of material.The Mn element is controlled in certain scope, and purpose is the intensity that increases matrix, and makes the stable performance of material.Therefore, control Mn:0.20-0.40% among the present invention, preferably control Mn:0.21-0.39%.
Cr:6.5-8.8%
Cr is the strong carbide forming element, can improve the hardening capacity of material, and is simultaneously cheap.But Cr also is the major cause that carbide network forms, and influences the toughness of material, so the content of Cr is unsuitable too high.The Cr that in the CrMoV steel, contains 11.0-13.0%; These Cr and C have formed netted ledeburite carbide; The carbide of these chromium is skewness in the crystallisation process of steel; Not only influenced the chromium element and promoted the effect of hardening capacity, and reduced the bending strength and the notched bar impact strength index of steel at steel grade.Suitably reduce Cr content, purpose is the homogeneous microstructure that makes material, improves the toughness of material.The content that has reduced Cr has on the other hand also reduced the manufacturing cost of alloying element simultaneously.Therefore, control Cr:6.5-8.8% among the present invention, preferably control Cr:6.55-8.75%.
Mo:1.2-1.3%,V:0.2-0.3%
Mo and V form second precipitate mutually of disperse in steel, the precipitate of these disperses not only can play the precipitation strength effect, and can hinder growing up of austenite crystal effectively, improves the obdurability of material.And because the avidity of Mo and V and carbon atom is strong, in drawing process, reduced martensitic decomposition rate, improved the stability of steel.Compare suitable raising Mo and V content with Cr12MoV, make tissue have more proeutectoid carbide disperse to separate out, make martensite that sufficiently high intensity arranged.Therefore, control Mo:1.2-1.3% among the present invention, V:0.2-0.3%; Preferably control Mo:1.21-1.29%, V:0.21-0.29%.
P<0.020%
Phosphorus is the harmful element in the steel, increases the fragility of steel, reduces the impelling strength of steel, so the more traditional cold-work die steel of phosphoric control is low, and the raising of performance index value is had certain effect.
S<0.020%
Element sulphur causes the deterioration of the processing characteristics of steel easily on certain degree, make steel in hot worked process, produce overheated and burn-off phenomenon easily.Therefore control the more original technological Cr12MoV steel of sulphur content lower can improve steel processing characteristics and mechanical property, the superheat that the continuous forging processing when particularly diameter is forged the machine hammer cogging is produced plays the effect of drawing up.
The present invention is through control appropriate C, Cr, Mo and V, to reduce and the refining eutectic carbide crystal grain thinning; Control an amount of Si; So that these compositions with an amount of Si solid solution in matrix, improve to consider the precipitation strength effect of the carbide of Cr and Mo and V, and formation sorbite tissue; Improve the hardness and the toughness of steel, and have good wear resistance.
This cold-work die steel impels alloying element to dissolve in matrix in a large number through after being heated to 1020 ℃ of-1040 ℃ of austenitizings, improves the alloy degree, strengthens solid solution strengthening effect.Simultaneously, in carrying out the double tempering process, disperse is separated out the tiny and uniform second phase particle through precipitation strength, improves the material obdurability.
Embodiment 1
In the present embodiment, the Composition Control value and the weight percent thereof that adopt high toughness wear resistant cold-work die steel chemical element proportioning to form are following:
C:0.90%, Si:0.55%, Mn:0.35%, Cr:8.80%, Mo:1.30%, V:0.30%, P:0.019%, S:0.013%, surplus is Fe.
In the present embodiment, the technological process and the step of cold-work die steel are following:
Adopt the steel ingot that carries out in the induction furnace being cast into after the melting to be positioned in the esr device as consumable electrode, carry out esr, liquid metal falls in the following water mold through the slag blanket of slag bath, is frozen into 2.0 tons of steel ingots more again; Above-mentioned steel ingot is heated in 1230 ℃ of TRs insulation forges processing after 4 hours; Initial forging temperature: 1100 ℃, 870 ℃ of final forging temperatures.
The treatment process temperature control of Q-tempering: 1030 ℃ of quenching temperatures; 200 ℃ of tempering temperatures
Adopt the hardness of the high toughness wear resistant cold-work die steel of present embodiment to reach HRC62.5, more universal cold-work die steel Cr12MoV is suitable; Impact toughness value 79J, more universal cold-work die steel Cr12MoV improves 103%.
The concrete chemical ingredients (weight percent) of embodiment 2-6 sees shown in the table 1 that processing parameter control is seen shown in the table 2.
The chemical ingredients of table 1 embodiment of the invention steel, Wt%
Embodiment |
C |
Mn |
Cr |
Si |
Mo |
V |
P |
S |
1 |
0.90 |
0.35 |
8.80 |
0.55 |
1.30 |
0.30 |
0.019 |
0.013 |
2 |
0.89 |
0.23 |
6.80 |
0.78 |
1.30 |
0.30 |
0.018 |
0.016 |
3 |
0.93 |
0.20 |
7.20 |
1.0 |
1.28 |
0.23 |
0.010 |
0.008 |
4 |
0.85 |
0.40 |
6.50 |
0.75 |
1.20 |
0.20 |
0.019 |
0.005 |
5 |
0.95 |
0.35 |
8.00 |
0.70 |
1.27 |
0.28 |
0.017 |
0.017 |
6 |
0.91 |
0.38 |
8.80 |
0.98 |
1.20 |
0.25 |
0.016 |
0.019 |
The main technique condition of table 2 embodiment of the invention steel
Test Example 1: metallographic structure
Fig. 1 is that steel of the present invention (embodiment 1) and CrMoV steel compare through the metallographic structure behind the Q-tempering.Fig. 1 (a) for steel of the present invention 1030 ℃ quench and 200 ℃ of tempering after metallograph.Find out among the figure and be uniform-distribution with the tiny carbide particle of disperse on the martensitic matrix.Such tissue guarantees that steel of the present invention has good combination of strength and toughness.Fig. 1 (b) is the metallograph of Cr12MoV steel.Find out in the picture that the segregation that has ledeburite carbide causes the decline of toughness of material.
Other embodiment have also obtained similar result.
Test Example 2:
According to the normal temperature ballistic work of GB/T229 method mensuration embodiment of the invention steel, according to the hardness of GB/T230.1 method mensuration embodiment of the invention steel, its result sees table 3.
The performance of table 3 embodiment of the invention steel
Embodiment |
Ballistic work J |
Hardness value (HRC) |
1 |
79 |
62.5 |
2 |
80 |
62.5 |
3 |
83 |
62 |
4 |
79 |
63 |
5 |
79.5 |
62.5 |
6 |
81 |
62 |
Test Example 3: wear resistance
Friction-wear test is carried out on MM-200 type wear testing machine, and specimen size is 3mm * 7mm * 30mm.Test parameter is under the unlubricated condition of room temperature, and load is 3kg, and to mill material: M2 (67.5-68HRC), rotating speed is 200r/m, and the time is 3 minutes.
Fig. 2 be steel of the present invention (embodiment 3) through 1040 ℃ quench and 210 ℃ of tempering after the histogram that compares of the wear resistance of the wear resisting property that detects and traditional cold-work die steel Cr12MoV.The hardness that shows two kinds of materials is suitable, and wear resistance of the present invention slightly is better than the Cr12MoV steel.Other embodiment have also obtained similar result.
Steel of the present invention is compared with the Cr12MoV steel, and alloying element content is low, has reduced manufacturing cost, has improved the competitiveness of product in market, and the rank of the distribution of the carbide in the microstructure of steel of the present invention and character carbide network all has greatly improved.Therefore under equal forging ratio condition, steel of the present invention can make more than Cr12MoV that the dendroid carbide morphology obtains better fragmentation in the tissue of as cast condition, and the microstructure of refinement steel improves the performance of steel.Steel rational chemical proportioning of the present invention makes the performance index of steel obviously promote with advanced ME.Traditional Cr12MoV Impact Toughness of Steel is 39J, and hardness is 60HRC.And steel of the present invention is through after 1030 ℃ of 200 ℃ of tempering heat treatment of quenching, and ballistic work is 79J, and hardness is 62HRC.Under identical wear resisting property situation, its impelling strength has improved 1 times.
During forming, Chemical Composition of the present invention contains segregation, a spot of Mo and V that lower carbon content reduced primary carbide form disperse in steel second precipitate mutually; The precipitate of these disperses not only can play the precipitation strength effect; And can hinder growing up of austenite crystal effectively, improve the obdurability of material.Steel of the present invention adopts the content that reduces carbon and chromium, and C and Cr are controlled in the reasonable range, adds carbide forming elements such as a spot of Mo, V, promptly can the highly malleablized matrix, played the purpose of controlling the cost of alloying element again.Carbide morphology under the cold-work die steel as cast condition is improved, thereby when forging, just can obtain carbide uniform distribution preferably with less forging ratio, that is to say can be so that carbide obtains better uniform distribution under the situation of identical forging ratio.Wear resisting steel hardening capacity of the present invention is good, and quenching temperature is lower, and heat treatment deformation is little, and price is low, has intensity and flexible cooperation preferably, is applicable to and makes the sophisticated die steel, can replace the general cold-work die steel of Cr12MoV type in the larger context.
Though abovely describe the present invention through specific embodiment; But be not limited only to these embodiment; Under the prerequisite that does not break away from the present invention's design, more changeableization or improved embodiment can also be arranged, and these variations and improvement all should belong to the scope of requirement of the present invention.